The present invention relates to an optical pickup device, and in particular, to an optical pickup device that is of a thin type and can conduct recording and/or reproducing of information properly for an optical information recording medium.
In recent years, research and development of high density optical disc system that can conduct recording and reproducing of information by using a blue-violet semiconductor laser having a wavelength of about 400 nm is advanced rapidly. As an example, in the case of an optical disc conducting recording and reproducing of information under the specifications of NA 0.85 and light source wavelength 405 nm, namely, in the case of the so-called Blu-ray Disc (BD), information in the amount of 20-30 GB can be recorded on a single face for an optical disc having a diameter of 12 cm that is the same in terms of size as DVD (NA 0.6, light source wavelength 650 nm, memory capacity 4.7 GB), and in the case of an optical disc conducting recording and reproducing of information under the specifications of NA 0.65 and light source wavelength 405 nm, namely, in the case of the so-called HD DVD, information in the amount of 15-20 GB can be recorded on a single face for an optical disc having a diameter of 12 cm. In the present specification, the optical disc of this kind is called “high density DVD” hereafter.
In the meantime, a value of an optical pickup device as a product is not sufficient if an ability of the optical pickup device is only conducting recording and reproducing of information properly for the high density DVD. When considering a reality at present that DVD and CD on which various pieces of information are recorded are on the market, only conducting recording and reproducing of information properly for high density DVD is not sufficient, an arrangement to be capable of conducting recording and reproducing of information properly in the same way also for conventional DVD or CD which has been owned by a user, for example, can enhance a value of an optical pickup device of a compatible type as a product. From the background of this kind, an optical system used for the optical pickup device of a compatible type is required to be of a low cost and to have a simple structure naturally, and to obtain an excellent spot for conducting recording and reproducing for information properly even for any of high density DVD, conventional DVD and CD. Though an optical pickup device capable of conducting recording and/or reproducing of information for DVD and CD on a compatible basis has been put into practical use, further downsizing, a thinner type and a low cost are demanded for the present structure of the optical pickup device. In particular, in the case of a notebook computer, there is an actual condition that a thinner type optical pickup device to be mounted on the notebook computer is desired eagerly, to enhance competitiveness of the product.
In Patent Document 1, there is disclosed an optical pickup device that conducts recording and/or reproducing of information under the state where the spherical aberration is corrected by moving a lens of a collimator optical system in the optical axis direction depending on an optical disc to be used to change an angle of divergence of a light flux passing through the lens. The lens of a collimator optical system of this kind is driven by a driving device that is relatively low in cost and is of a small-sized structure.
A piezoelctric element serving as a power source for an actuator shown in Patent Document 1 has characteristics that an amount of generated heat is small, when compared with other actuators. However, when an optical pickup device is constituted to be extremely thin, the piezoelctric element is occasionally arranged to be close to an optical element for the reason of a space. In such a case, there is a fear that the optical element is affected by heat generated from the piezoelctric element, especially when the optical element is made of resin.                (Patent Document 1) Unexamined Japanese Patent Application No. 2005-302118        